Investigation On Wear Behavior And Transformation Of Ti-6Al-4V

With the development of titanium alloy technology,the reduction of production cost and use restrictions,the application threshold of titanium alloy is reduced.Therefore,the focus of its use has shifted from aerospace and military to medical,biological ship engineering equipment and other fields of life.But at the same time,because of its relatively poor wear resistance,although it has other excellent mechanical properties,its use is still limited.Therefore,it is of great significance to explore the wear properties of titanium alloy.Because the use environment is more at room temperature,we need to establish the research system of wear properties of titanium alloy at room temperature.The main content of this study is to grind Ti-6Al-4V titanium alloy pin on disc at room temperature.The friction speed is 0.2-4.0m/s,and the loading load is 10-240 N.The wear rate is measured by friction and wear experiment,and the wear rate load curve is drawn.The surface morphology is analyzed by SEM,and the surface element content is analyzed by EDS Mechanism transformation diagram.The changes of surface hardness and cross-section morphology were compared and analyzed.The microstructure changes of subsurface layer were observed and analyzed.The gradient hardness curves of cross-section under different sliding speeds and different loads were measured.The wear change of Ti-6Al-4V alloy can be divided into two stages: mild wear and severe wear.These two stages are important criteria for us to determine whether Ti-6Al-4V alloy can work safely.When the sliding speed is 0.2m/s,the wear mechanism is abrasive wear and mild oxidation wear,and the severe wear stage is abrasive wear and severe oxidation wear.When the sliding speed is 0.5m/s,the wear mechanism is the same as that when the sliding speed is 0.2m/s.At the sliding speed of 0.785 m/s-2.0 m/s,the wear mechanisms in the slight wear stage are abrasive wear,delamination wear and adhesive wear,and severe plastic deformation occurs in the severe wear stage.In the sliding speed range of 2.0 m/s-4.0 m/s,with the increase of load,the delamination wear in the slight wear stage transits rapidly to the severe plastic deformation in the severe wear stage.The results show that the wear mechanism is different in the severe wear stage above 0.785 m/s.In order to compare and analyze the changes of surface microstructure and properties after slight severe wear transition,surface hardness test,section microstructure observation and section hardness test were carried out respectively.The wear surface hardness is analyzed under the conditions of 0.2 m/s,0.785 m/s and2.0 m/s,and the curve features are similar to each other.The wear surface hardness will decrease with the increase of load.The turning point of hardness decrease corresponds to the turning point of mild and severe wear.The analysis of cross-section microstructure shows that the surface microstructure changes from plastic deformation to dynamic recrystallization before and after slight severe wear.At the same sliding speed,with the increase of loading load,the gradient hardness of the section decreases until the matrix hardness,and the surface layer shows strain strengthening induced by plastic deformation.During severe wear,the gradient hardness of the cross-section will decrease in a certain width valley within a certain depth from the worn surface,resulting in softening phenomenon,which is caused by the dynamic recrystallization transformation of the worn surface.The wear rate load curves of Ti-6Al-4V alloy and Mg97Zn1Y2 alloy at 20 ℃,50 ℃,100 ℃,150 ℃ and 200 ℃ were measured.The worn surface morphology was analyzed.The wear mechanism before and after slight severe wear transition was revealed.The critical load of slight severe wear transition of Ti-6Al-4V alloy and Mg97Zn1Y2 alloy at 20-200℃ was compared.